Recently, awareness of the importance of safe data storage and retainment has been being heightened and demands for the disaster recovery system have been increasing in a data storage market. When some failure occurs at a data storage base, where data is stored (hereinafter referred to as the data center), and a system stops, the disaster recovery system is a system for switching services to another system to continue the services and minimizing the damage caused by the system stop.
Conventionally, the disaster recovery system where two data centers are provided and the two points are connected has been realized. However, if the disaster recovery system is constructed at the two data centers and a failure occurs at one data center, only the other data center continues services, thereby increasing a load and significantly degrading performance.
So, PTL 1 discloses a technique to construct a disaster recovery system at three or more data centers. The disaster recovery system of PTL 1 guarantees data ordinality and eliminates data inconsistency by taking over the data update status between the data centers.